Assembling apparatus for rolling and clamping a part to a tubular member

ABSTRACT

This invention relates to a finned assembly for a heat exchanger comprising an extended surface portion, an elongated tubular member, said extended surface portion comprising two identical parts, each having an internal cylindrical surface adapted to engage said tubular member and each having radially extending locking members adapted to engage locking members on the other of said parts. The invention further relates to methods and apparatus for attaching said extended surface portion to said member.

States Patet 1 l 1 9 9 Tibbetts et al. May 29, 1973 ASSEMBLING APPARATUSFOR [56] References Cited ROLLING AND CLAMPING A PART TO A TUBULARMEMBER UNITED STATES PATENTS Inventors: Alan R Tibbetts, Costa Mesa;Bruegger D 392 2 Lakewood both Primary Examiner-Thomas H. EagerAttorney-Edmund W. Bopp and H. Hume Mathews [73] Assignee: Airco, Inc.,New York, NY. 22 Filed: Feb. 7, 1972 [57] ABSTRACT [21] pp No: 224,320This invention relates to a finned assembly for a heat exchangercomprising an extended surface portion, an Related s A li i Dataelongated tubular member, said extended surface portion comprising twoidentical parts, each having an in- [62] DlVlSlOl'l of Ser. No. 792,593,Jan. 21, 1969, Pat. No. terna] cylindrical Surface adapted to engage dmbw lar member and each having radially extending v locking membersadapted to engage locking members [52] US. Cl. ..29/202 D, 29/DIGl 32 onthe other of Said parts. The invention further Int. Cl. lates to methodsand apparatus for hi g Said [58] Field of Search ..29/202 D, 202 R,

29/DIG. 32, 200 B, 202.5

tended surface portion to said member.

5 Claims, 12 Drawing Figures PATENIw M29 1m SHEET 1 [IF 4 PAIENI W919SHEET 2 OF 4 FIG. 6B

PATENTEB MAY 2 9 I973 SHEET 3 0F 4 Pmtmmww 3.735.465

SHEET l 0F 4 ASSEMBLING APPARATUS FOR ROLLING AND CLAMPING A PART TO ATUBULAR MEMBER This is a division of application Ser. No. 792,593,

.filed Jan. 21, 1969, now U.S. Pat. No. 3,672,446

granted June 27, 1972.

This invention relates to an improved form of ambient air vaporizer madeof dissimilar materials which are joined together without welding. Thevaporizer constructed according to the invention is capable ofwithstanding high vapor pressure and has excellent heat transfercharacteristics.

The use of various forms of ambient air vaporizers is well known in thecryogenic industry. The ambient air vaporizers are known to take theform of aluminum castings in the form of blocks which may beinterconnected for the passage of the cryogenic fluid being heated. Inanother well known construction the vapor izer takes the form ofelongated sections of extended surface material which are formed fromaluminum extrusions. Extrusions are generally star-shaped with aplurality of radially extending fins and with a central opening throughwhich the cryogenic fluid passes. The extrusion is usually made fromaluminum alloy 6063-Tl and the extrusion is made in an'elongated lengthwhich is then cut up into desired lengths. In its most common form theextrusions are placed in a block with four sections on a side and eachsection is interconnected with the next in a series of parallel orcombination thereof (as desired) arrangement by means of bent tubingwhich is welded to interconnect the central openings of the aluminumextrusions so that fluid may be transmitted into one end of theextrusion and through the opening which passes through the interior ofthe extrusion and thus out the other end through the exit tubing. Theexit tubing is serially connected by welding to an adjacent extrusionand the cryogenic liquid is thereby passed from one section to the nextuntil it has passed through all 16 sections. Such ambient air vaporizersare often used with customer stations which include a liquid storagetank in which the liquified gas is stored, and a high pressure liquidpump which pulls the suction on the liquid storage tank and directs thehigh pressure liquid output to the ambient air vaporizer. The vaporizermay take the form of any of the vaporizers discussed above and may ofcourse also take the form of the invention as it will be described inmore detail hereinbelow. From the vaporizer the gaseous product isdirected to a use point such as for example a steel mill, aluminum'remelt furnace or perhaps be directed into a gas cylinder fillingmanifold. In order to assist in the heat transfer process a blower maybe placed so that it directs ambient air across the vaporizer. Thenecessity for such a blower would of course depend upon the rate ofvaporization desired and the climactic conditions involved.

In the prior art form of ambient air vaporizer which may be describedfor purposes of discussion as the star type, it has been found thatnumerous instances of failure of the critical welds have occurred. Thefailures occur due to the fact that the tubing which connects thevaporizer sections must be welded to the ends of the vaporizer sectionsin such a manner so as to withstand thousands of pounds of pressure. Ingeneral the tubing interconnecting the vaporizer sections is made ofbent aluminum tubing and the vaporizer sections themselves are made ofextruded aluminum. The welds joining these two elements must thereforebe made with a high degree of skill so as to be entirely fluid tight andso as to be able to withstand high internal vapor pressure. In aconventional customer station a normal anticipated pressure of 3,000 psior more is reached in the vaporizer. In the most commonly used ambientair vaporizer bank 16 sections are utilized. It is therefore apparentthat at least 32 welds are required to join and interconnect the tubingwith the extruded sections. As mentioned above each individual weld mustbe carefully made and must then be closely inspected and hydrotested inorder that it be able to withstand the rigors of cryogenic service. Itis evident that the degrees of expansion and contraction of dissimilarlyshaped metal parts vary. Thus as the low temperature cryogenic liquidwhich for purposes of example might be liquid nitrogen at 320 F, flowsthrough the tubing and through the extruded sections, the various partsof the ambient air vaporizer will contract at various rates. This willcause the welds which interconnect the various portions to be placedunder additional stresses. The ambient air vaporizers are often cycliclyutilized and the stresses and strains which are undergone by the weldsinterconnecting the portions can often cause failure of the welds. Thusthe technique of welding the sections to the interconnecting piping hasbeen found to be an extremely costly method of manufacture and hasfurther been found to produce an unreliable product.

Thus it has been found that although the prior art form of ambient airvaporizer is widely used in thefield, it embodies various structural anddesign concepts which leave much to be desired.

This invention relates to a heat exchanger structure and to a method andapparatus for manufacturing the same which alleviates all of theabove-mentioned defects in the prior art form of ambient air vaporizer.It is an object of the present invention to provide an ambient airvaporizer utilizing extruded aluminum extended fin surfaces coupled to astainless steel conduit which passes through the extended fin section.It is a further object of the present invention to couple the extrudedaluminum sections to the stainless steel tubing without any welds.

It is a further object of the present invention to provide apparatus forlocking identical sections of extruded aluminum extended surfacematerial about an elongated conduit.

Other and further objects of this invention will become apparent tothose skilled in this art from the following detailed description on theannexed sheets of drawings, which by way of preferred example,illustrate several embodiments of the invention.

In the drawings:

FIG. 1 is a view partly in perspective of an ambient air vaporizercoupled with'a schematic showing of a conventional customer station.

FIG. 2 is a perspective view, partly broken away, partly in section of aconventional ambient air vaporizer section made of extruded aluminum.

FIG. 3 is an end view of an extrusion formed in accordance with thepreferred form of the invention.

FIG. 4 is an end'view, partly in cross section, partly broken awayshowing a pair of identical extrusions locked to a conduit in accordancewith the preferred form of the invention.

FIG. 5 is an end view, partly in section, partly broken away, of a pairof extrusions about to be coupled together in accordance with theprinciples of another embodiment of the present invention.

FIG. 6A is a cross sectional view of an extruded ambient air vaporizersection about to be coupled to a conduit in accordance with theprinciples of a still further embodiment of the present invention.

FIG. 6B is an end view, partly in section, partly broken away, of astill further embodiment of the present invention.

FIG. 7 is a plan view, partly broken away, of apparatus for lockingtogether the sections of ambient air vaporizer made in accordance withthe present invention.

FIG. 8 is an elevational view, partly broken away, of the apparatusshown in FIG. 7.

FIG. 9 is an end view, partly in section, partly broken away, of thevaporizer sections and conduit being locked together in a first lockingoperation in a first set of forming rolls.

FIG. 10 is an end view, partly in section, partly broken away, of asecond set of forming rolls completing the locking of the extrudedaluminum sections to the tubular conduit.

FIG. 11 is an end view, partly in section, partly broken away, of astill further embodiment of the inventron.

In FIG. 1 there is illustrated an ambient air vaporizer bank 10 which isconnected to a cryogenic storage tank 11 by means of conduit 12. A pump13 suitable for pumping a cryogenic liquid forces high pressurecryogenic liquid into the ambient air vaporizer bank 10. If the storagetank 11 contains for example liquid nitrogen, the temperature of thenitrogen entering the ambient air vaporizer bank is approximately 320 F.The cryogenic liquid passes serially through the sections of the bank 10wherein the liquid is vaporized and the resulting vapor exits throughconduit 14. The delivery pressure of the cryogenic vapor is normallycontrolled by a pressure regulator 15 and both the storage tank 11 andthe delivery conduits 12 and 14 are normally supplied with conventionalrelief valves, shut-off valves and coupling connections which are notshown. In a typical nitrogen customer station the pumping system andvaporizer are capable of supplying 5,000 SCFI-I at 3,000 psi to the usepoint. The size of the vaporizer 10, pump 13 and storage tank 11 wouldof course depend upon the amount of vapor that must be delivered to theuse point. The illustration in FIG. 1 is not to scale. Persons skilledin the art will recognize that normally the storage tank is considerablylarger than the vaporizer structure. The vaporizer bank is normallyenclosed in a framework indicated generally by the reference numerals l6and 17. In the prior art form of ambient air vaporizer, the fins of thevaporizer sections were directly connected to the frameworks 16 and 17in order to structurally mount the bank in the framework. As will bediscussed in greater detail below, the present invention calls forconnecting the tubing to the frameworks 16 and 17. This greatlystrengthens the entire vaporizer bank 10 in view of the fact that thestainless steel tubes are directly connected to the steel housings l6and 17.

Depending upon the desired output of the ambient air vaporizer bank 10it may be necessary to install a blower indicated by the referencenumber 20 to blow ambient air over the vaporizer bank. By forcing airover the vaporizer bank, additional output of the vaporizer may beobtained.

The details of the storage tank 11, which is normally vacuum insulated,and of the pumping system 13 are not provided in this disclosure in thatthey form no part of the present invention and in view of the fact thatmany different types of tanks and pumping systems are availablecommercially.

In FIG. 2 there is illustrated a perspective view of a conventionalambient air vaporizer section coupled in the conventional fashion toaluminum tubing by a continuous annular weld 28. In the conventionalstar type vaporizer there are eight radially extending fins 25 whichemanate from a central annular hub 26 having a hollow interior 27. Thisstructure is normally extruded aluminum. The cryogenic liquid passes inthe first instance from the conduit 12 into the interior 27 wherein itis warmed up as it passes through the extruded section. Note that thestar configuration provides a large surface area per unit of length ofthe section thus resulting in high heat transfer to the cryogenicliquid. Upon the completion of welding the tubing to the extrusion theweld must be stress-relieved in the conventional manner by a heatingprocess or extremely heavy-walled tubing must be employed. Similarly, aconduit comparable to conduit 12 is connected to the other end of thesection and is welded in the same manner as discussed above inconnection with weld 28. Thus a weld must be made at each end of thevaporizer section. If the vaporizer bank contains 16 vaporizer sections,at least 32 welds will have to be made to interconnect the sections withsuitable tubing. To withstand the high vapor pressure, the wallthickness of the aluminum tubing must be considerably thicker than thewall thickness of stainless steel tubing designed to withstand acomparable pressure.

In FIG. 3 there is illustrated an end view of one part of an ambient airvaporizer section built in accord with the preferred form of theinvention. The part which is indicated by the reference numeral 35 isformed of extruded aluminum and is normally used in standard lengths of6 feet. The part comprises a pair of radially extending fins 36 and 37which are connected to a central hub 38 by means of fin portions 39 and40 respectively. The fin portions 39 and 40 are of a greater thicknessthan the fin portions 36 and 37 in that they support fins 36 and 37 andfins 42 and 43. The extra thickness also provides improved heat transfercharacteristics.

The fins 42 and 43 have been formed as an extension of fins 36 and 37due to the fact that the portion of the hub 38 which would normallysupport the fins 42 and 43 is now used to support locking members whichwill now be described.

Each of the fins 42 and 43 is made of two parts, a radial part 48, 49and an offset part 46,47. The radial part lies along a radius extendingfrom the longitudinal axis of the vaporizer section and the offsetportion diverges from the radius and is interconnected with the adjacentfin 36 or 37. It can be observed from FIG. 3 that the included anglebetween fins 36 and 37 is 45 and the included angle between fin 37 andthe radial part 49 of fin 43 is also 45. The same may be said for theradial part of fin 42 and the fin 36. The angle between the radial fins36, 37 and offset part 47, 46 is preferably as close to 45 as possiblewithout interfering with the locking members before, during or after theforming process.

It has been found that an angle of 45 between adjacent fins on anambient air vaporizer is preferred due to the fact that the frostbuild-up which inevitably occurs on the fin surfaces does not bridgeover between adjacent fins when the angle is approximately45. If theincluded angle between the fins is less than about 40, it has been foundthat the frost bridges between the two fins starting at the root of theangle and then proceeding radially outwardly. A frost build-up of coursesubstantially reduces the desired heat transfer characteristics of theair vaporizer. If the included angle is greater than approximately 45,the number of tins and thus the surface area must be reduced.

The hub 38 comprises a substantially annular portion 51 with an interiorpartly cylindrical surface 52. Projecting from the annular member 51 butformed integral therewith are a pair of locking members 53 and 54. Thelocking member 53 will be described as the short locking member and themember 54 described as the long locking member in the interest ofdefining the invention. The short locking member 53 takes in part theform of a partly cylindrical surface 58. The surface 58 preferably hasan approximately 90 arc. The outermost end of the locking member 53 isrounded off at 59 and this somewhat diminishes the said arc, and thepurpose for this will be discussed below. The locking member 53 furthercomprises an interior partially cylindrical surface 60 which isconcentric with the cylindrical surface 58. The radius defining thecylindrical surface 60 is preferably one-half the radius defining thecylindrical surface 58. As shown in FIG. 3, the partially cylindricalsurface 60 has a 180 arc.

The long locking member 54 is also formed from an extension of the hub38 and is integral therewith. The last-mentioned locking member includesa base portion 62 which extends in preferably the opposite directionfrom the extension defined by the locking member 53. The base member 62is slightly longer than the total extension of the fixed locking member'53 as indicated by the fact that the dimension A shown on FIG. 3 isgreater than the comparable dimension B. The reason for this will bediscussed below.

The outer portion 64 of the locking member 54 is formed at 90 to thebase member 62 during the extrusion process. Theinterconnection betweenthe outer member 64 and the base member 62 is formed with roundedsurfaces 65 and 66 in order that the outer member 64 may be bentinwardly toward the hub 38 without the interconnection fracturing orotherwise failing. In the preferred form of the invention the outermember 64 is formed slightly longer than the base member 62. Note thatthe outermost extremities of the outer member 64 are also rounded off67, 68. It has been found that by rounding surfaces of aluminum which isto be bent or otherwise shaped, metal failures are often avoided.

It is to be noted that the interior cylindrical surface 52 of the hub 38is formed with a cylindrical surface which is less than one-half thefull cylindrical surface (less than a 180 arc). The reasons for thusforming the surface 52 will be described below in connection with theassembly of the extruded parts and the conduit tube.

By utilizing two identical vaporizer parts as illustrated in FIG. 3 andby positioning the two parts in the manner which will now be describedabout a fluid carrying conduit composed of a similar or dissimilar metaland by interlocking the locking members of the two identical parts aunitary ambient air vaporizer section may be formed without thenecessity for making any welds. The end product is illustrated in FIG.4. By mating the cylindrical surfaces 52 of the separate parts with theexterior cylindrical surface 70 of the conduit 71 and by bending overthe outer members 64 of the long locking member to engage the shortlocking member 53 of the opposite part, the two identical parts may beaffixed in good heat transfer relationship to the conduit 71.

The apparatus for accomplishing this step will be discussed in detailbelow. The bending or forming actually takes place in the two-stageforming rolls in one operation. In the first stage the outer member 64is bent at a 45 angle with respect to the base member 62. This bringsthe inner surface 72 of the outer member 64 of one part in contact withthe arcuate surface 58 of the fixed locking member 53 of the other part.In a subsequent forming stage the outer member 64 is forced stillfurther inwardly toward the base member 62. The first" forming step isillustrated clearly in FIG. 9 and the second-forming step is indicatedin FIG. 10. By forcing the locking member 64 even further inward in thesecond step it is caused to conform to the exterior curved surface 58 ofthe fixed locking member 53. This results in the clamping of the partstogether about the tubing or conduit 71 and causes the cylindricalsurfaces 52 to conform to the exterior cylindrical surface 70 of theconduit 71. By having these surfaces conform to one another and bycausing substantially complete contact between the surfaces 52 and 70throughout the length of the section optimum heat transfercharacteristics are realized.

In forming the interior partly cylindrical surface of the hub 38 aradius is utilized which slightly exceeds the radius of the externalcylindrical surface of the tubing or conduit 71. For example, if theradius of the tubing is 0.625 inches the radius of the hub will beapproximately 0.65 inches. This is done for a number of rea sons. Due tothe nature of the extrusion process tolerances on extruded parts arenormally greater than on comparable parts made by other processes(machining, etc Therefore, we have designed the internal radius to beslightly oversize. Furthermore, it has been found that if the radius ofthe hub 38 slightly exceeds the radius of the outer cylindrical surfaceof the tube, the hub will be better able to conform to the surface ofthe exterior of the tube. In the preferred form of the invention thetubing is stainless steel and therefore the extruded aluminum willconform to the surface of the harder stainless steel.

Thus when the locking members are forced over one another, thecylindrical surface 52 is able to closely conform to the outercylindrical surface of the tubing so as to minimize the thermal contactresistance between the tubing and the hub. If the radius of the arcuateportion 52 were smaller than the radius of the conduit (or undersized),the hub 38 would not as readily conform to the surface of the conduit.It is therefore preferable to design the hub to be slightly over-sizedso that the extrusion tolerances can be taken into consideration and sothat the hub will always readily conform to the tubing.

The arcuate portion 58 of the short locking member 53 is formed so thatthe outer member 64 of the adjacent vaporizer part will be able to bendarcuately about the short member. This is done in order to reduce sharpbends in the member 64 which would be subject to failure. The dimensionA of base member 62 is of course greater than the dimension B of theshort member 53 in order that the outer member 64 may clear the roundedsurface 59 and be formed around the short member 53. Arcuate surface 60of short member 53 is formed in order that the thickness indicated bythe dimension C is equal to the thickness of the long locking member 54,indicated by the dimension D. This is done in order that the spring backforces which will result from the forming process will be equal in boththe short and long locking members. By causing the spring back forces tobe substantially equal, the locking members will play an essentiallyequal role in generating the clamping force on the tubing. Thus whencryogenic liquid is pumped through the tubing 71 and the stainless steelconduit contracts slightly due to its low temperature, the spring backforces will maintain the cylindrical surfaces 52 in contact with theexterior surface 70 of the conduit. This inherent resiliency in ourlocking technique therefore allows for variations in tolerances and forvariations in dimension caused by cryogenic temperature. The methods andapparatus for forming will be discussed in detail below following thediscussion of other embodiments of the invention.

In FIG. there is illustrated a further embodiment of the presentinvention which utilizes a pair of identical vaporizer parts 80 whichare to be locked about a fluid carrying conduit. The hub 81 of each ofthe parts is formed with substantially oppositely extending lockingmembers 82, 83. On one surface of each of the locking members 82 and 83there are formed serrations or projections indicated by 84. In thepreferred form the inner cylindrical surface 85 is formed with an areslightly less than 180. A pair of identical parts 80 are placed aroundthe conduit 86 in such a manner that the locking projections 83 and 84lie alongside adjacent locking projections on the adjacent part. Whenthis has been done a locking clamp 89 is forced over each pair ofadjacent locking members and the locking clamp 89 is drivensubstantially radially inwardly so that the locking members are clampedtogether. The clamp 89 is formed with inner serrations or projections 90which pass over the serrations 84 and which are so angled so as toprevent the removal of the clamp 89 from the locking members 83 and 84when the clamp is fully seated thereon. In the embodiment shown in FIG.5 the inner radius of the hub 81 is again made to be slightly largerthan the radius of the exterior of the conduit 86 so as to obtain thesame result as discussed above in connection with FIG. 4. Thus theclamps 89, which may be forced on by form rolling, exert a resilientclamping force on the hubs 81 so that they conform to the surface of thetubing. The parts 80 may be made from extruded aluminum sections and thelocking clamps 89 may also be made from aluminum.

In FIG. 6A there is illustrated a still further embodiment of thepresent invention in which the hub 90 is formed of one piece and issplit as indicated at 91 in a longitudinal direction. The hub 90 has anarc slightly less than 360 (25). A pair of lugs 92 and 93 are formedintegral with the hub and extend substantially radially from the portionwhich has been split. A clamping mechanism 94 is adapted to engage theradially extending lugs 92 and 93 and by this device the hub is clampedto the tubing 102. The clamping device 94 is preferably as long as thehub section 90 so that a clamping force on the lugs 93 and 92 will beexerted substantially along the entire length of the hub 90. Theclamping member 94 has an I beam configuration with projecting lugs 95and 96 which lock about the lugs 92 and 93 on the hub. By forcing thearms 98, 99 of the I beam apart as indicated by 97, the lugs 95 and 96can be made to contact seats 100 and 101 to force the lugs 92 and 93toward one another, thus clamping the hub 90 about the tubing 102. Theconduit 102 is actually slid into the hub 90 before the clamping deviceis applied. The clamping device, which is preferably made from aluminumis also slid into position on the hub prior to clamping. As in the caseof FIGS. 4 and S the internal radius of the hub is made slightly greaterthan the radius of the external cylindrical surface of the conduit 102for the reasons stated above.

In FIG. 6B there is illustrated a still further embodiment of thepresent invention. The vaporizer section 140 is formed from a singleextrusion, the hub 141 being split longitudinally at 142. In thisembodiment the clamping force on the conduit 143 is exerted by the hub141 itself. The split portion of the hub is forced open slightly toallow the insertion of the conduit 143. When the conduit is fullyinserted the hub is allowed to close around the conduit 143. Portions146 and 147 constitute locking members which wrap around the conduit.The inherent spring back characteristics of the hub keep it locked tothe conduit. In this embodiment the internal radius of the hub 141 ispreferably the same as or slightly smaller than the radius of theexternal surface of the conduit. Due to the hardness of the stainlesssteel conduit, the softer inner aluminum surface of the hub readilyconforms to the conduit to obtain good heat transfer.

In FIG. 7 there is illustrated an apparatus for forming the ambient airvaporizer described in connection with FIG. 4. The apparatus takes theform of a suitable supporting stand 103 on which is mounted a drivemechanism 104 and a plurality of bearing assemblies which rotatablysupport four shafts, 105 through 108. Directly beneath the shafts 105and 106 are shafts 107 and 108. All of the shafts are drivably connectedto a drive means inside drive housing 104. This housing contains a motorconnected to suitable gearing, etc., for rotating the upper shafts 105and 106 in the same direction and at the same speed. The drive mechanismdrives the lowermost shafts 107 and 108 at the same speed and in thesame direction but in a direction opposite to that of the upperdriveshafts 105 and 106. Guide plates 109 and 110 are vertically mountedon the supporting stand 103 and are positioned to guide the vaporizerparts and the associated tubular conduit into the forming rollersindicated by the reference numerals and 121. Two pairs of formingrollers are utilized each having an upper forming roller and a lowerforming roller, as illustrated in FIG. 8. Each of the forming rollers iscomposed of a plurality of interlocked wheellike members of varyingradius and configuration.

In assembling the ambient air vaporizer described in FIG. 4 theidentical parts are positioned around the central conduit tube and thelocking members are placed in a substantially vertical position. Theassembly is then placed on guide plate 109 in such a manner that one ofthe outer members 64 rests on the surface of the guide plate 109. Theassembly is then slid along the plate 109 and is passed between theforming rollers 120 and 122. The locking members are engaged by formingrolls and 126 as indicated in FIG. 9. The radial tip portions of thevaporizer fins engage portions of the forming rolls 127 through 130 asshown at 150-157. By contacting the tips of the vaporizer fins with theforming rolls as shown, the vaporizer parts are held in place while themain forming rollers 125 and 126 form the outer member 64 about thefixed locking member 53. The first set of forming rollers encounteredbend the outer members 64 45 and into contact with the arcuate surfaceof the fixed locking member. The next set of forming rollers which thevaporizer section encounters is located directly behind the formingrolls indicated in FIG. 8. This set of forming rolls completes thebending of outer members 64 so that they fully conform to the arcuatesurface 72 on the fixed locking member. The shape of the forming rollsfor accom plishing this is indicated in FIG. 10. They have a channelshaped groove 144 which further bends the outer member 64 inwardly.Supporting rolls (158-161) similar to those disclosed in FIG. 8 (127through 131)) are used with the second set of forming rollers to supportthe radial tips of the fins.

As the vaporizer section leaves the second set of forming rolls andrides on guide plate 110, it can be inspected to determine whether ornot the forming has been completely accomplished and whether or not theidentical parts of extended surface material are completely fixed to theconduit in the manner desired. The drive mechanism 104 is therefore madereversible in order that, if desired, the sections of vaporizer may berun back and forth through the rolling mechanism. The

' details of the drive mechanism and of the bearing structure supportingthe shafting for the roll forming mechanism have not been described indetail in that they are conventional in nature.

A roll-forming mechanism comparable to that disclosed in FIGS. 7 throughmay be utilized to assemble the embodiment disclosed in FIG. 5 and inFIG. 6A. That is, forming rollers force clamping devices 89 over thelugs 83, 84 which extend from the hub section of the vaporizer. In FIG.6A a roller may be used to force arms 9% and 99 apart.

In FIG. 11 there is illustrated a still further embodiment of thepresent invention. Identical parts 160 and 161 are formed fro m extrudedaluminum and are clamped about a tubular conduit 162. Each part is madeup of a hub portion 163 and two locking members, a partially cylindricalrecess 164, and a snap lock 165. The snap is formed from an extension ofthe hub and has a rod shaped element 166 which snaps into the recess164. The connection between the element 166 and the hub has sufficientflexibility and resiliency to allow the element to snap into the recessand thus the two parts 160 and 161 may be placed around the conduit 162and snapped in place. The internal radius of the hub 163 is madeslightly greater than that of the conduit 162 for the same reasons asstated above in connection with FIGS. 41, 5 and 6A. Thus the parts 160and 161 are resiliently coupled to the conduit. Forming rollers may beutilized to affect the snap coupling of the embodiment shown in FIG. 11.By forcing the parts together as shown by the arrows the snap connectionmay be made.

When the vaporizer sections have been assembled as described above, theymay be mounted in a supporting framework so that they may be transportedand mounted at a customer station. It is evident that since stainlesssteel conduit is used and since a steel framework is usually employed toform the supporting structure, the stainless steel conduit may beaffixed by means of clamps or struts to the supporting structure of theframework. In the embodiments shown the aluminum extended fin surfaceexpands and contracts at will without affecting the structural mountingbetween the tubing and the support structure. In all of the embodimentsthe aluminum fin structure may expand or contract radially or axially atwill but will always conform itself to the exterior surface of thestainless steel tube.

It has been found beneficial to coat the entire surface of each of thealuminum parts with a thin layer (0.00l-0.l00 inch) of fluorocarbonmaterial such as for example, Teflon, Coracone, Dynar, etc. This coatingpresents a very good appearance, substantially reduces the frost-upwhich normally occurs, and has been found to only slightly reduce theanticipated heat transfer rate of the vaporizer. The coating may even beapplied to the internal cylindrical surface of the hub in that the layeris so thin that only a temperature drop of 1 or from has beenencountered across this tiIrn. The fluorocarbon film is mechanicallystrong and touch, resistant to low temperature, and to most chemicalsand solvents and as mentioned above, greatly reduces the frost-upencountered in this type of unit.

The present invention may be utilized not only with the manufacture ofambient air vaporizers, but with the manufacture of any other device orstructure calling for the attaching of one part to the outside ofanother part. Thus the invention may be used in the manufacture of manytypes of heat exchangers. It may be used to couple insulation ordecorative material to piping or conduits.

To those skilled in the art to which our invention relates, many changesin construction and widely differing embodiments and applications of theinvention may suggest themselves without departing from the spirit andscope of the invention. Our disclosure and the description herein arepurely illustrative and are not intended to be in any sense limiting.

We claim:

1. Apparatus for clamping extended suface material comprising at leastone part to a tubular member to form an assembly comprising, a support,a pair of forming rollers rotatably mounted on said support, means todrive said rollers in opposite directions, support means to guide saidat least one part and member between said forming rollers, each of saidrollers com-prising forming means for clamping said at least one partabout said member.

2. The apparatus of claim 1 having a second pair of forming rollersmounted on said support, said second rollers having forming means forfurther clamping said at least one part about said member,

3. The apparatus of claim 1 having reversing drive means for reversingthe direction of the forming rollers.

about said member.

i I l:

1. Apparatus for clamping extended surface material comprising at least one part to a tubular member to form an assembly comprising, a support, a pair of forming rollers rotatably mounted on said support, means to drive said rollers in opposite directions, support means to guide said at least one part and member between said forming rollers, each of said rollers comprising forming means for clamping said at least one part about said member.
 2. The apparatus of claim 1 having a second pair of forming rollers mounted on said support, said second rollers having forming means for further clamping said at least one part about said member.
 3. The apparatus of claim 1 having reversing drive means for reversing the direction of the forming rollers.
 4. The apparatus of claim 1 in which each of said forming rollers comprises a plurality of wheel like members of different diameters having portions adapted to engage a plurality of points on said at least one part to support the same as the forming takes place.
 5. The apparatus of claim 1 in which each of said forming rollers has a wheel like member having a peripheral recess adapted to enGage and clamp said part about said member. 